High efficiency ferrite antenna system

Abstract

An automatic tuning procedure can be used to allow a small, high efficiency ferrite antenna assembly to be used in various FM frequency based devices. The ferrite antenna can take the form of a rod or flat disk, for example, which can use a pick-up coil and tuning coil to provide sufficient signal strength using a small FM antenna. A balanced amplifier can be used to provide differential input in order to further reduce noise. A microcontroller can determine the strength of the FM signal at various frequencies and can automatically tune the operating frequency to optimize system performance.

1. An antenna assembly for use with an FM frequency device, comprising:
 a ferrite rod; 
 a single turn tuning coil wound about a first portion of the ferrite rod, the single turn tuning coil operable to receive a tuning frequency and adjust the resonant frequency of the ferrite rod in response thereto; and 
 a multi-turn pick-up coil wound about a second portion of the ferrite rod, the multi-turn pick-up coil capable of having a voltage induced thereon by a received FM signal at the adjusted resonant frequency, the multi-turn pick-up coil being further configured to provide the received FM signal as output. 
 
     
     
       2. An antenna assembly according to  claim 1 , wherein:
 the at least one of the tuning and pick-up coils is formed of a copper tape. 
 
     
     
       3. An antenna assembly according to  claim 1 , wherein:
 the ferrite rod is about 1 inch in length. 
 
     
     
       4. An antenna assembly according to  claim 1 , wherein:
 the multi-turn pick-up coil further includes a tap allowing the output to be applied to a pair of differential amplifiers. 
 
     
     
       5. An antenna assembly according to  claim 1 , wherein:
 the ferrite disk is about 40 mm in length and about 40 mm in width. 
 
     
     
       6. An antenna assembly for use with an FM frequency device, comprising:
 a substantially flat ferrite disk; and 
 a pick-up coil placed around a periphery of the ferrite disk, the pick-up coil capable of having a voltage induced thereon by a received FM signal at a resonant frequency of the ferrite disk, the pick-up coil being further configured to provide the received FM signal as output. 
 
     
     
       7. An antenna assembly according to  claim 6 , further comprising:
 a tuning coil positioned about the periphery of the ferrite disk, the tuning coil operable to receive a tuning frequency and adjust the resonant frequency of the ferrite disk in response thereto. 
 
     
     
       8. An antenna assembly according to  claim 7 , wherein:
 the pick-up coil is formed of a copper tape. 
 
     
     
       9. An antenna assembly according to  claim 7 , wherein:
 the pick-up coil is formed of a metal frame.